The disease caused by the variant Creutzfeldt-Jakob disease is linked to: MCQ with Answer and Explanation

Explanation:
Photoperiodism is the response of plants to the relative lengths of day and night, influencing flowering. Short-day plants (e.g., poinsettia) flower when day length is less than a critical period; long-day plants (e.g., spinach) flower when days are longer. Phototropism is growth towards light, geotropism to gravity, chemotropism to chemicals.

Explanation:
Meristem culture, a type of tissue culture, involves excising the virus-free apical meristem (shoot tip) and growing it on a nutrient medium to produce a whole plant free of viruses. This is because meristematic cells lack vascular connections through which viruses spread. Cloning produces identical copies, hybridization crosses varieties, mutagenesis uses mutagens.

Explanation:
Synovial fluid is a viscous, egg-white-like fluid secreted by the synovial membrane in synovial joints (e.g., knee, hip). It lubricates articular cartilage, reducing friction and wear, and also nourishes cartilage. CSF cushions CNS, pleural fluid reduces lung friction, aqueous humor is in the eye.